[New-bugs-announce] [issue25556] Fixes for PyObject_GetItem()

[STINNER Victor]

New submission from STINNER Victor:

Attached patch adds assertions to PyObject_GetItem() to ensure that an exception is raised if the function failed. _Py_CheckFunctionResult() could be used to implement such check, but it might adds a little overhead, whereas I really don't think that such bug occurs in the wild. The assertion only helps when you develop a new custom type implementing the mapping API.

The patch also simplifies Python/ceval.c: it now considers that an exception is raised if PyObject_GetItem() returns NULL.

Finally, the patch also fixes a bug in the LOAD_NAME bytecode, when globals are not a dict but a custom type and the name doesn't exist in globals: clear the exception before calling PyObject_GetItem() on builtins.

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components: Interpreter Core
messages: 254094
nosy: haypo, serhiy.storchaka
priority: normal
severity: normal
status: open
title: Fixes for PyObject_GetItem()
versions: Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue25556>
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